Nature of PMMA dissolution process by mixtures of acetonitrile/alcohol (poor solvent/nonsolvent) monitored by FTIR-imaging

The dissolution process of poly(methyl methacrylate), PMMA, in mixtures of the binary systems: acetonitrile/alcohol (methanol, ethanol and 1-propanol), individually poor and nonsolvents respectively for the polymer, was studied at 25 °C using FTIR imaging spectroscopy. To investigate this cosolvency phenomenon and the kinetics of the dissolution process, the spatial resolution and sensitivity of FTIR imaging were used. It has been found that the PMMA dissolution rate anomalously increases almost in a parabolic way independently of the solvent system used in this study. These results were interpreted assuming that the dissolution of a polymer by a mixture of solvents is governed by a complex dependence of the solvent molecules size and their thermodynamic characteristics. The kinetics of the PMMA dissolution by AcN/alcohol solvent mixtures were interpreted using conventional Arrhenius behavior in which the activation energy has a simple dependence on the thermodynamic quality and the molecular weight of the solvent mixture.